Field of the Invention
This invention relates to the field of signal transmission, and in particular, it relates to a long distance signal transmission device and related method for high definition multimedia interface.
Description of Related Art
Recent rapid technological developments are bringing wide use of multimedia audiovisual technologies around the globe. For example, multimedia technologies such as home theater 3D, Blu-ray technology, etc. are becoming available. With the fast growth of multimedia audiovisual entertainment products, functions such as multimedia audiovisual playback, touch screen capabilities, high quality communication services etc. are becoming popular trends for various electronic products. These advancements in multimedia technologies bring changes to new generations of audiovisual multimedia electronic products. Therefore, innovative multimedia audiovisual transmission technologies are an important aspect of multimedia audiovisual technologies.
High Definition Multimedia Interface (HDMI) is an all digital video and audio transmission interface which can transmit uncompressed audio and video signals. HDMI interface can be used in products such as set-top boxes, DVD players, personal computers, video game devices, integrated amplifiers, digital audio and television, etc. HDMI technologies are licensed to be used by over 1200 manufacturers; globally, over 1 billion consumer electronic devices use HDMI technologies, making HDMI a mainstream interface for multimedia transmission. HDMI can simultaneously transmit audio and video signals. Because audio and video signals use the same transmission cable, rather than using multiple transmission cables as in conventional transmission technologies, wire management is greatly simplified. For consumers, HDMI technology not only can provide clear and high quality images, because audio and video signals use the same cable, it can also simplify home theater systems and reduce difficulties in system installation.
When using HDMI to transmit multimedia audiovisual signals, the main signal transmission technology used is Transition Minimized Differential Signaling (TMDS). TMDS is a high speed data transmission technology developed by Silicon Image Inc. of the U.S.A., and can be used in DVI and HDMI audiovisual transmission interfaces. TMDS has four channels, the first three are respectively YU(Pb)V(Pr) transmission channels, or they can be considered RGB transmission channels, and the fourth channel is a clock signal channel, to provide a unified clock used for signal transmission. When transmitting signals using HDMI, various video and audio data are packaged by the HDMI transceiver chip into data packets using TMDS technology.
In other words, the transmission framework of HDMI audiovisual signal transmission includes, the end that transmits the TMDS signal is the transmitting end, the end that receives the TMDS signal is the receiving end, and the main connections are three pairs of TMDS data channels and one pair of TMDS clock channel. When the receiving end is connected to the transmitting end, after the transmitting end detects the Hot Plug Detect (HPD) signals, it reads data in the Extended Display Identification Data (EDID) via the Data Display Channel (DDC). EDID includes, for example, information regarding capabilities of the receiving end, information regarding the manufacturer, manufacturing date, the resolution supported by the receiving end, etc. The transmitting end then starts to transmit TMDS signals.
Generally speaking, the maximum transmission speed of each channel of HDMI technology is 165 MHz (4.95 Gb/s). With the improvement of HDMI transmission technologies, the bandwidth of HDMI is gradually increasing. For example, for HDMI Versions 1.0-1.2a, the maximum TMDS bandwidth is the above-mentioned 4.95 Gb/s; for Version 1.3, the maximum TMDS bandwidth is 10.2 Gb/s; and for Version 1.4, the maximum TMDS bandwidth is also 10.2 Gb/s. For version 2.0, the maximum TMDS bandwidth is 18 Gb/s, which can support quite large video bandwidth (14.4 Gb/s), audio bandwidth (49.152 Mb/s); compared to Version 1.0, it can support more different functions and channels, such as Ethernet channel, audio return channel, 3D Over HDMI, support for 4K×2K resolution, enhanced support for color space depth, Micro HDMI connector, etc.
Standard HDMI performance can satisfy the requirements of most consumers. The cable performance can support 74.5 MHz, and maximum reliable transmission of 1080i or 720p signals is 15 meters. On the other hand, high speed HDMI cables can achieve even higher performance levels, to meet requirements of high-end home theater systems, where the cable performance can support 340 MHz, and can reliable transmit signals (and higher definition signals) as far as 7.5 meters. Because of higher requirement of HDMI bandwidth, the HDMI speed instead limits the HDMI transmission distance. Whether for standard HDMI cable or high speed HDMI cable, the maximum transmission distance is still limited; this range limit is one of the main problems in its application. To transmit HDMI signals over longer distances, electrical cables cannot be used; fiber optic cables can be used instead, by converting electrical signals to optical signals, and converting optical signals back to electrical signals at the receiving end. Because optical signals can be transmitted over much longer distances, currently, while many options are available for transmission under 100 meters, HDMI devices for transmission over 100 meters typically use fiber optic cables to extend signal transmission range.
Refer to FIG. 1, which schematically illustrates long distance signal transmission devices for high definition multimedia signals according to conventional technologies. Such conventional devices for long distance signal transmission, for transmitting HDMI 2.0 signals, includes an HDMI transmitter 901 and an HDMI receiver 902. The HDMI transmitter 901 includes HDMI input interface 911, HDMI receiver chip 912, field-programmable gate array (FPGA) main processor chip 913, high-speed signal processor chip 914, and photoelectric module 915. The HDMI receiver 902 includes photoelectric module 925, FPGA main processor chip 923, HDMI transmitter chip 922, high-speed signal processor chip 924, and HDMI output interface 921. The signal from a signal source is inputted via the HDMI input interface 911, and transmitted by HDMI receiver chip 912 to the FPGA main processor chip 913; the FPGA main processor chip 913 re-packages the data and transmits the data packets to the high-speed signal processor chip 914 and photoelectric module 915. The data packets are transmitted via the optical fibers over a long distance to the photoelectric module 925 of the receiver; the data packets are unpackaged back to the original signal by the high-speed signal processor (synthesizer) chip 924 and the FPGA main processor chip 923, and transmitted to the HDMI output interface 921.
In the above conventional HDMI long distance signal transmission devices, the FPGA chip is typically very costly, and the main design cost of the system are the cost of the FPGA chips and the high speed signal processor and synthesizer chips. For example, for HDMI 2.0, its bandwidth is about 18 Gb/s, and requires two sets of FPGA combined; and to further increase transmission bandwidth, it is required to increase the high speed circuits of the of FPGAs and the signal synthesizer chips. Thus, the complexity and cost of the devices will increase. Moreover, because the FPGAs need to process large amount of packaging and un-packaging of packets, it will cause a reduction in signal transmission quality.